HLT31507 CERTIFICATE III IN NUTRITION
& DIETETIC ASSISTANCE
THE LYMPHATIC & IMMUNE SYSTEM
delivered by:
Mary-Louise Dieckmann
The Lymphatic System
• Consists of two semi-independent parts
– Lymphatic vessels
– Lymphoid tissues and organs
• Lymphatic system functions
– Transports escaped fluids back to the blood
– Plays essential roles in body defense and
resistance to disease
Lymphatic Vessels
• Lymphatic collecting vessels
– Collect lymph from lymph capillaries
– Carry lymph to and away from lymph nodes
– Return fluid to circulatory veins near the heart
• Right lymphatic duct
• Thoracic duct
Regional
lymph nodes:
Cervical
nodes
Axillary
nodes
Entrance of right
lymphatic duct into right
subclavian vein
Internal jugular vein
Thoracic duct
entry into left
subclavian vein
Thoracic duct
Aorta
Spleen
Inguinal
nodes
Cisterna chyli (receives
lymph drainage from
digestive organs)
Lymphatics
KEY:
Drained by the right lymphatic duct
Drained by the thoracic duct
Figure 12.3
Characteristics
• Lymph—excess tissue fluid carried by
lymphatic vessels
• Properties of lymphatic vessels
– One way system toward the heart
– No pump
– Lymph moves toward the heart
• Milking action of skeletal muscle
• Rhythmic contraction of smooth muscle in vessel walls
Venous
system
Arterial
system
Heart
Lymph duct
Lymph trunk
Lymph node
Lymphatic
system
Lymphatic
collecting
vessels,
with valves
Lymph
capillary
Tissue fluid
(becomes
lymph)
Blood
capillaries
Loose connective
tissue around
capillaries
Figure 12.1
Lymphatic Vessels
• Lymph Vessels (Lymph Capillaries)
– Walls overlap to form flap-like mini valves
– Fluid leaks into lymph capillaries
– Capillaries are anchored to connective tissue by
filaments
– Higher pressure on the inside closes mini valves
– Fluid is forced along the vessel
Tissue fluid
Tissue cell
Lymphatic
capillary
Blood
capillaries
Arteriole
Venule
(a)
Figure 12.2a
Fibroblast in loose
connective tissue
Flaplike
minivalve
Endothelial
cell
(b)
Filaments
anchored to
connective
tissue
Figure 12.2b
Lymph
• Harmful materials that enter lymph vessels
includes:
– Bacteria
– Viruses
– Cancer cells
– Cell debris
Lymph Nodes
• Filter lymph before it is returned to the blood
• Defense cells within lymph nodes
– Macrophages—engulf and destroy foreign
substances
– Lymphocytes—provide immune response to
antigens
Regional
lymph nodes:
Cervical
nodes
Axillary
nodes
Entrance of right
lymphatic duct into right
subclavian vein
Internal jugular vein
Thoracic duct
entry into left
subclavian vein
Thoracic duct
Aorta
Spleen
Inguinal
nodes
Cisterna chyli (receives
lymph drainage from
digestive organs)
Lymphatics
KEY:
Drained by the right lymphatic duct
Drained by the thoracic duct
Figure 12.3
Afferent
lymphatic
vessels
Germinal
center in
follicle
Capsule
Subcapsular
sinus
Trabecula
Afferent
lymphatic
vessels
Cortex
Follicle
Efferent
lymphatic
vessels
Hilum
Medullary sinus
Medullary cord
Figure 12.4
Flow of Lymph Through
Nodes
• Lymph enters the convex side through afferent
lymphatic vessels
• Lymph flows through a number of sinuses
inside the node
• Lymph exits through efferent lymphatic
vessels
• Fewer efferent than afferent vessels causes
flow to be slowed
Other Lymphoid Organs
• Several other organs contribute to lymphatic
function
– Thymus
– Spleen
– Peyer’s patches
– Tonsils
Tonsils (in
pharyngeal region)
Thymus (in thorax;
most active during
youth)
Spleen (curves
around left side of
stomach)
Peyer’s patches
(in intestine)
Appendix
Figure 12.5
Thymus Gland
• Located low in the throat, overlying the heart
• Functions at peak levels only during childhood
• Produces hormones (like thymosin) to
program lymphocytes (T Cells)
Spleen
•
•
•
•
Located on the left side of the abdomen
Filters blood
Destroys worn out red blood cells
Returns iron to the liver for hemoglobin
production
• Acts as a blood reservoir
Peyer’s Patches
• Found in the wall of the small intestine
• Resemble tonsils in structure
• Capture and destroy bacteria in the intestine
Tonsils
• Small masses of lymphoid tissue around the
pharynx
• Trap and remove bacteria and other foreign
materials
• Tonsillitis is caused by congestion with
bacteria
Mucosa-Associated Lymphatic
Tissue (MALT)
• Includes
– Peyer’s patches
– Tonsils
– Other small accumulations of lymphoid tissue
• Acts as a sentinel to protect respiratory and
digestive tracts
Body Defenses
• The body is constantly in contact with
bacteria, fungi, and viruses
• The body has two defense systems for foreign
materials
– Nonspecific (innate) defense system
– Specific (adaptive) defense system
• Together they make up the immune system
Body Defenses
• Nonspecific defense system
– Mechanisms protect against a variety of invaders
– Responds immediately to protect body from
foreign materials
• Specific defense system
– Specific defense is required for each type of
invader
– Commonly referred to as the immune system
Body Defenses
Figure 12.6
Nonspecific Body Defenses
• Body surface coverings
– Intact skin
– Mucous membranes
• Specialized human cells
• Chemicals produced by the body
Defensive Cells
• Phagocytes
(neutrophils and
macrophages)
– Engulfs foreign
material into a
vacuole
– Enzymes from
lysosomes digest the
material
Figure 12.7a
Events of
Phagocytosis
Figure 12.7b
Inflammatory Response Second Line of Defense
• Triggered when body tissues are injured
• Produces four cardinal signs
– Redness, Heat, Swelling and Pain
• Results in a chain of events leading to protection and
healing
Functions of the
Inflammatory Response
• Prevents spread of damaging agents
• Disposes of cell debris and pathogens
• Sets the stage for repair
Steps in the
Inflammatory
Response
Figure 12.8
Fever
• Abnormally high body temperature
• Hypothalmus heat regulation can be reset by
pyrogens (secreted by white blood cells)
• High temperatures inhibit the release of iron
and zinc from liver and spleen needed by
bacteria
• Fever also increases the speed of tissue repair
Specific Defense: The Immune
System – Third Line of Defense
• Antigen specific – recognizes and acts against
particular foreign substances
• Systemic – not restricted to the initial
infection site
• Has memory – recognizes and mounts a
stronger attack on previously encountered
pathogens
Types of Immunity
• Humoral immunity (B cells)
– Antibody-mediated immunity
– Cells produce chemicals for defense
• Cellular immunity (T cells)
– Cell-mediated immunity
– Cells target virus infected cells
Antigens (Non-self)
• Any substance capable of exciting the immune
system and provoking an immune response
• Examples of common antigens
–
–
–
–
–
–
Foreign proteins
Nucleic acids
Large carbohydrates
Some lipids
Pollen grains
Microorganisms
Active Immunity
• Your B cells
encounter antigens
and produce
antibodies
• Active immunity
can be naturally or
artificially acquired
Figure 12.14
Passive Immunity
• Antibodies are obtained from someone else
– Conferred naturally from a mother to her fetus
– Conferred artificially from immune serum or
gamma globulin
• Immunological memory does not occur
• Protection provided by “borrowed antibodies”
Organ Transplants and
Rejection
• Major types of grafts
– Autografts – tissue transplanted from one site to
another on the same person
– Isografts – tissue grafts from an identical person
(identical twin)
– Allografts – tissue taken from an unrelated person
– Xenografts – tissue taken from a different animal
species
Organ Transplants and
Rejection
• Autografts and isografts are ideal donors
• Xenografts are not very successful
• Allografts are more successful with a closer
tissue match
Disorders of Immunity:
Allergies (Hypersensitivity)
• Abnormal, vigorous immune responses
• Types of allergies
– Immediate hypersensitivity
• Triggered by release of histamine from IgE binding to mast cells
• Reactions begin within seconds of contact with allergen
• Anaphylactic shock – dangerous, systemic response
Disorders of Immunity:
Allergies (Hypersensitivity)
• Types of allergies (continued)
– Delayed hypersensitivity
• Triggered by the release of lymphokines from activated
helper T cells
• Symptoms usually appear 1–3 days after contact with
antigen
Disorders of Immunity:
Immunodeficiencies
• Production or function of immune cells or
complement is abnormal
• May be congenital or acquired
• Includes AIDS – Acquired Immune Deficiency
Syndrome
Disorders of Immunity:
Autoimmune Diseases
• The immune system does not distinguish
between self and non-self
• The body produces antibodies and sensitized T
lymphocytes that attack its own tissues
Disorders of Immunity:
Autoimmune Diseases
• Examples of autoimmune diseases
– Multiple sclerosis – white matter of brain and spinal cord
are destroyed
– Myasthenia gravis – impairs communication between
nerves and skeletal muscles
– Juvenile diabetes – destroys pancreatic beta cells that
produce insulin
– Rheumatoid arthritis – destroys joints